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Abstract:

An application for a flow control system includes a tapered plunger
situated within an conduit. The conduit is open to a downstream drainage
system. The tapered plunger is buoyant, assisted by one or more floats
attached such that, when the water level around the flow control system
increases to a predetermined level above a top rim of the conduit, the
tapered plunger lifts due to the buoyancy. In such, the flow rate is
maintained substantially constant. At the emergency level, alternate
drain systems provide increased drainage to reduce the potential of
flooding.

Claims:

1. A flow control system for integration into a detention pond, the flow
control system comprising:a stationary riser, the stationary riser having
a stationary riser hollow core, an axis of the stationary riser hollow
core being vertical, a top end of the stationary riser has a rim and the
opposing end of the stationary riser is open and leads to a drainage
system;a tapered plunger, the tapered plunger fitting in place within the
stationary riser hollow core defining a gap area between an outer surface
of the tapered plunger and an inner surface of the stationary riser
hollow core, whereas liquid from the detention pond flows over the rim,
through the gap area, through the hollow core and into the drainage
system; andat least one float interfaced to the tapered plunger, the at
least one float providing buoyancy to the tapered plunger.

2. The flow control system of claim 1, wherein the stationary riser is
held within an aperture in a cover of a holding box and the rim is level
with a top surface of the cover.

3. The flow control system of claim 1, wherein the stationary riser is
held within an aperture in an internal shelf of a holding box.

4. The flow control system of claim 1, wherein the at least one float
consists of two buoyant members interfaced to the tapered plunger by
shafts.

5. The flow control system of claim 1, wherein the at least one float
consists of three buoyant members interfaced to the tapered plunger by
shafts.

6. The flow control system of claim 5, wherein the shafts provide a means
for adjusting a height of the buoyant members with respect to the tapered
plunger.

7. The flow control system of claim 1, further comprising a stop to
prevent the tapered plunger from lifting out of the stationary riser
hollow core.

8. A flow control system for integration into a detention pond, the flow
control system comprising:a holding box, the holding box installed in a
bed of the detention pond, the holding box having an interior cavity and
at least one opening in fluid communication with a liquid contained in
the detention pond;a stationary riser, the stationary riser having a
stationary riser hollow core, an axis of the stationary riser hollow core
being substantially vertical, a top end of the stationary riser having a
rim, the top end of the stationary riser held within an aperture in a lid
covering the holding box, liquid flowing through the stationary riser
hollow core exiting the holding box through a drainage system;a tapered
plunger, the tapered plunger fitting within the stationary riser hollow
core to form a gap area between an inner surface of the stationary riser
hollow core and an outer surface of the tapered plunger; andat least one
float interfaced to the tapered plunger, the at least one float providing
buoyancy to the tapered plunger;whereas liquid from the detention pond
flows over the rim, through the gap area, through the stationary riser
hollow core and into the drainage system.

9. The flow control system of claim 8, wherein the at least one float
consists of two buoyant members interfaced to the tapered plunger by
shafts.

10. The flow control system of claim 8, wherein the at least one float
consists of three buoyant members interfaced to the tapered plunger by
shafts.

11. The flow control system of claim 10, wherein the shafts provide a
means for adjusting a height of the buoyant members with respect to the
tapered plunger.

12. The flow control system of claim 8, further comprising a stop to
prevent the tapered plunger from lifting out of the stationary riser
hollow core.

13. The flow control system of claim 8, further comprising a bypass drain,
a top rim of the bypass drain situated at a higher elevation than the rim
of the stationary riser and the bypass drain is in fluid communication
with the drainage system.

14. A flow control system for integration into a detention pond, the flow
control system comprising:a holding box, the holding box installed in a
bed of the detention pond, the holding box having an interior cavity, a
shelf, and at least one opening located above the shelf and in fluid
communication with a liquid contained in the detention pond;a stationary
riser, the stationary riser having a stationary riser hollow core, an
axis of the stationary riser hollow core being substantially vertical, a
top end of the stationary riser having a rim, the top end of the
stationary riser held within an aperture in the shelf, liquid flowing
through the stationary riser hollow core exits the holding box through a
drainage system;a tapered plunger, the tapered plunger fitting within the
stationary riser hollow core to form a gap area between an inner surface
of the stationary riser hollow core and an outer surface of the tapered
plunger; andat least one float interfaced to the tapered plunger, the at
least one float providing buoyancy to the tapered plunger;whereas liquid
from the detention pond flows over the rim, through the gap area, through
the stationary riser hollow core and into the drainage system.

15. The flow control system of claim 14, wherein the at least one float
consists of two buoyant members interfaced to the tapered plunger by
shafts.

16. The flow control system of claim 14, wherein the at least one float
consists of three buoyant members interfaced to the tapered plunger by
shafts.

17. The flow control system of claim 16, wherein the shafts provide a
means for adjusting a height of the buoyant members with respect to the
tapered plunger.

18. The flow control system of claim 14, further comprising a stop to
prevent the tapered plunger from lifting out of the stationary riser
hollow core.

19. The flow control system of claim 14, further comprising a bypass
drain, a top rim of the bypass drain situated at a higher elevation than
the rim of the stationary riser and the bypass drain is in fluid
communication with the drainage system.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001]This is related to U.S. patent titled "FLOW CONTROL SYSTEM FOR A
DETENTION POND," attorney docket 2664.4, inventor Jonathan D. Moody,
filed even date here within. This is also related to U.S. patent
application Ser. No 12/463,614, filed May 11, 2009, attorney docket
2664.3 and inventor Jonathan D. Moody; the disclosure of which is herein
incorporated by reference.

FIELD OF THE INVENTION

[0002]The disclosure relates to the field of flow control devices and more
particularly to a flow control device for a detention pond or surge tank.

BACKGROUND

[0003]Detention ponds and surge tanks are deployed to temporarily store a
fluid and limit the rate of fluid discharge to a downstream system when
the inflow rate of the fluid is variable at times exceeds the functional
capacity of the downstream system. In the case of a storm water detention
pond, the pond receives increased rates of storm water runoff generated
by the development of upstream lands, temporarily stores the runoff and
limits the rate of discharge of the runoff to a receiving system of water
conveyance such as a river, stream or storm sewer such that the capacity
of the receiving system is not exceeded thereby causing flooding, harmful
erosion or other environmental damage. Similarly, a surge tank
temporarily stores a process fluid of varying inflow rate and limits the
rate of discharge of the fluid to that which will not exceed the capacity
of a downstream process. In the field of wastewater treatment, a surge
tank may be deployed to receive wastewater flows during peak periods of
water use, temporarily store the wastewater and limit the release of the
wastewater flow to the treatment plant to a rate not exceeding the design
capacity of the plant.

[0004]The temporary storage volume required for a detention pond or surge
tank is dependent on the rate and duration of fluid inflow and the
allowable rate and duration of fluid outflow. The larger the difference
between the peak rate of inflow and the allowable rate outflow, the
greater the volume is required for temporary storage. Whereas providing
large storage volumes can be costly such as the expense incurred for land
acquisition and excavation required to construct a large detention pond
or the expense of fabrication and installation of a very large tank it is
therefore advantageous to minimize the amount of temporary storage volume
required for safe operation of the system. Minimization of the temporary
storage volume required can be accomplished by minimizing the difference
between the duration and rate of inflow and the duration and rate of
outflow. Since the rate inflow is variable and cannot be controlled,
minimization of the required temporary storage volume is achieved when
the maximum allowable rate of discharge is sustained for the longest
possible duration of time.

[0005]The prior art is generally concerned with limiting the maximum
outflow rates, at which damage can occur, by employing discharge control
mechanisms such as fixed weirs, orifices, nozzles and riser structures
whereby the maximum discharge rates of such mechanisms are determined by
the geometric configuration of the mechanisms and the height of the fluid
or static head acting on the mechanisms. In each case, the maximum flow
rate is achieved only at the single point in time at which the static
head acting on the mechanism is at its maximum level. Therefore, all
discharges occurring when fluid levels are not at their maximums are less
than optimum.

[0006]One solution to this problem is described in U.S. Pat. No. 7,125,200
to Fulton, which is hereby incorporated by reference. This patent
describes a flow control device that consists of a buoyant flow control
module housing an orifice within an interior chamber that is maintained
at a predetermined depth below the water surface. This flow control
device neglects the use of other traditional flow control mechanisms such
as weirs, risers and nozzles, has limited adjustability, and utilizes
flexible moving parts subject to collapse by excess hydrostatic pressure
or failure resulting from material fatigue caused by repeated cyclical
motion.

[0007]What is needed is a flow control device that provides for deployment
of a variety of discharge control mechanisms in singular or in
combination, is readily adjustable to accommodate for deviations incurred
during installation, settlement, or by variability in the weights and
densities of the materials of which it is comprised and does not rely on
parts subject to failure by excess hydrostatic force or repeated cyclical
motion while maintaining a nearly constant rate of discharge at varying
fluid levels.

SUMMARY

[0008]A flow control system of the present invention includes a tapered
plunger situated within a conduit, thereby creating a gap between the
conduit and the tapered plunger through which water or other fluids flow
and eventually reach a downstream drainage system. The tapered plunger
lifts due to buoyancy, thereby reducing the area of the gap between the
tapered plunger and the bottom edge of the conduit. The cross sectional
area of the tapered plunger increases as the water level increases and is
a function of the orifice equation such that the cross sectional area of
the tapered plunger Ap=Ai-[Q/C(2gH)2]where:

[0009]Q=constant flow rate

[0010]H=Effective head on the orifice/gap

[0011]C=Orifice coefficient of discharge

[0012]Ai=Cross Sectional Area of inside of conduit

[0013]Ap=Cross Sectional Area of the tapered plunger

[0014]Bouyancy of the tapered plunger is assisted by one or more floats
attached such that, when the water level around the flow control system
increases to a pre-determined level above a top rim of the conduit, the
tapered plunger lifts due to the buoyancy. In such, the flow rate is
maintained substantially constant until the water level reaches a
predetermined emergency level. At the emergency level, alternate drain
systems provide increased drainage to reduce the potential of flooding.

[0015]In one embodiment, a flow control system for integration into a
detention pond or surge tank is disclosed including a stationary riser
having a core that has an axis that is substantially vertical. A top end
of the stationary riser has a rim and the opposing end of the stationary
riser is open and empties to a drainage system. A tapered plunger fits in
place within the hollow core defining a gap area between an outer surface
of the tapered plunger and an inner surface of the stationary riser
hollow core and liquid from the detention pond flows over the rim,
through the gap area, through the hollow core and into the drainage
system. There is at least one float interfaced to the tapered plunger,
providing buoyancy to the tapered plunger.

[0016]In another embodiment, a flow control system for integration into a
detention pond or surge tank is disclosed including a holding box
installed in a bed of the detention pond. The holding box has an interior
cavity and at least one opening in fluid communication with a liquid
contained in the detention pond. A stationary riser that has a hollow
core, an axis of which being substantially vertical, has a top end held
within an aperture in a lid covering the holding box. Liquid flowing
through the stationary riser hollow core exits the holding box through a
drainage system. A tapered plunger fits within the hollow core to form a
gap area between an inner surface of the stationary riser hollow core and
an outer surface of the tapered plunger. There is at least one float
interfaced to the tapered plunger, providing buoyancy to the tapered
plunger. Liquid from the detention pond flows over the rim, through the
gap area, through the stationary riser hollow core and into the drainage
system.

[0017]In another embodiment, a flow control system for integration into a
detention pond or surge tank is disclosed including a holding box
installed in a bed of the detention pond. The holding box has an interior
cavity, a shelf, and at least one opening that is in fluid communication
with a liquid contained in the detention pond and is located above the
shelf. A stationary riser has a hollow core, an axis of which being
substantially vertical. A top end of the stationary riser has a rim and
is held within an aperture in the shelf so that liquid flowing through
the stationary riser hollow core exits the holding box through a drainage
system. A tapered plunger fits within the stationary riser hollow core to
form a gap area between an inner surface of the hollow core and an outer
surface of the tapered plunger and at least one float is interfaced to
the tapered plunger, providing buoyancy to the tapered plunger. Liquid
from the detention pond flows over the rim, through the gap area, through
the stationary riser hollow core and out through the drainage system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]The invention can be best understood by those having ordinary skill
in the art by reference to the following detailed description when
considered in conjunction with the accompanying drawings in which:

[0019]FIG. 1 illustrates a sectional view of a system of the system of a
first embodiment of the present invention.

[0020]FIG. 2 illustrates a detail sectional view of the system of the
first embodiment of the present invention.

[0021]FIG. 3 illustrates sectional view of a system of a second embodiment
of the present invention.

[0022]FIG. 4 illustrates a perspective view of a system of a second
embodiment of the present invention.

[0023]FIG. 5 illustrates a perspective view of a system of the second
embodiment of the present invention.

[0024]FIG. 6 illustrates a sectional view of a system of the system of a
third embodiment of the present invention.

[0025]FIG. 7 illustrates a sectional view of a system of the system of a
fourth embodiment of the present invention.

DETAILED DESCRIPTION

[0026]Reference will now be made in detail to the presently preferred
embodiments of the invention, examples of which are illustrated in the
accompanying drawings. Throughout the following detailed description, the
same reference numerals refer to the same elements in all figures.
Throughout the following description, the term detention pond and surge
tank represent any such structure and are equivalent structure for
detaining liquids. Throughout this description and claims, the terms
detention pond and/or surge tank are interchangeable and represent any
body of liquid.

[0027]The flow control system described provides for an initial discharge
rate starting as soon as the detention pond or surge tank reaches a
pre-determined liquid level, then, as the liquid level increases, the
discharge rate and the down-stream water pressure remain relatively
constant until a high-water level is reached, at which level the flow
control system provides for an increased discharge rate to reduce the
possibility of exceeding the volumetric capacity of the detention pond or
surge tank. Throughout this description, the detention pond is referred
to as holding a liquid. Such liquid is often referred to as water, but is
not limited to water and often contains other materials, other liquids
and other solids such as salts, oils, leaves, silt and other debris.

[0028]Prior to more advanced flow control systems, limiting the maximum
outflow rates at which damage can occur was accomplished by deploying
discharge control mechanisms such as fixed weirs, orifices, nozzles and
riser structures whereby the maximum discharge rates of such mechanisms
are determined by the geometric configuration of the mechanisms and the
height of the fluid or static head acting on the mechanisms. In each
case, the maximum flow rate is achieved only at the single point in time
at which the static head acting on the mechanism is at its maximum level.
Therefore, all discharges occurring when fluid levels are not at their
maximums are less than optimal and require provision of greater temporary
storage capacities. The present invention solves these and other problems
as is evident in the following description.

[0029]By initiating a maximum flow rate through the described system once
the water level reaches a pre-determined level and continuing that flow
rate until the water level reaches a level that is of, for example, flood
stage, the detention pond will empty faster than one using a system in
which the maximum flow rate is achieved only just before the water level
reaches the flood stage (e.g. the water level is below maximum when the
water level reaches the pre-determined level). In such, using the system
of the present invention reduces the overall capacity requirements for
the detention pond, thereby reducing the land area needed to support the
detention pond, etc.

[0030]Referring to FIG. 1, a schematic view of a system of the present
invention will be described. The detention pond or surge tank flow
control system 20 has two primary components, a holding box 26 and the
actual flow control device 40. The holding box is shown in FIG. 1 with an
optional lid 28 and optional debris shield 30.

[0031]The holding box 26 and optional lid 28 is typically made of concrete
or metal. The debris shield 30 partially covers an opening 32 in the side
of the holding box 26 to reduce influx of leaves, oil and other debris
from the liquid 10 in the detention pond as the liquid 10 flows into the
holding box 26. The holding box 26 is positioned part way into the bed 12
of the detention pond 10. As the liquid level 9 in the detention pond 10
rises, it is skimmed by the debris shield 30, holding back some or all of
any floating debris, oil, etc, and the liquid (e.g. water) from the
detention pond or surge tank spills over into the holding box 26 through
the opening 32.

[0032]The flow control device 40 consists of a stationary riser or conduit
42 and a movable plunger 46 (see FIG. 2). Details of the movable plunger
46 are shown in FIG. 2. Once the liquid level 9 within the holding box 26
rises above the top rim 48 of the stationary riser 42, liquid flows over
the top rim 48 at a constant rate independent of the liquid level of the
detention pond or surge tank 10 because the bottom of the movable plunger
46 is held at approximately the same depth beneath the liquid surface 9
within the holding box 26. The liquid flows through the stationary riser
42 and out the drain pipe 24 to the drainage system, streams, rivers,
etc. in the case of a storm water detention pond or downstream process in
the case of, for example, a surge tank.

[0033]Although the flow control system 40 is capable of supporting itself
within the holding box 26, it is anticipated that one or more optional
struts 44 are provided to secure the flow control system 40 to the
holding box 26. In addition, also anticipated is a bypass drain 22, which
begins bypassing water when the liquid level 9 in the detention pond or
surge tank 10 reaches a certain height such as a flood height.

[0034]In some embodiments, a lock (not shown) is provided to lock the
cover 28 on top of the holding box 26.

[0035]Referring to FIG. 2, a detail sectional view of the system 40 of the
first embodiment of the present invention including the plunger 46 will
be described. The floats 50/52 are shown affixed to float shafts 54/56
which are affixed to cross members 60/62. The cross members 60/62 are
affixed to a plunger shaft 55 and the plunger shaft 55 is affixed to the
movable plunger 46.

[0036]The movable plunger 46 is positioned within a hollow core of a
stationary riser or conduit 42 and the stationary riser or conduit 42 is
in fluid communications with a drain conduit 24 that interfaces to the
drainage system. Although not required, it is preferred that the
cross-sectional shape of the movable plunger 46 be similar to the
cross-sectional shape of the conduit 42. For example, the cross sectional
shape of a movable plunger 42 is circular having an outer diameter less
than the inner diameter of the conduit 42. In this way, the liquid 10
(e.g. rain water) flowing over the lip 48 of the conduit 42 will flow
past the movable plunger 46 and out through the drain conduit 24.

[0037]The flow control mechanism 40 provides an approximately constant
discharge rate through the drain conduit 24 by maintaining a constant
depth, d, between the surface level 9 of the liquid 10 and the bottom 47
of the movable plunger 46. The discharge rate is proportional to the
distance d between the surface 9 of the liquid 10 and the bottom 47 of
the movable plunger; and a gap area which is the space between the outer
surface 45 of the movable plunger 46 and the inner wall 41 of the
stationary riser or conduit 42. If the movable plunger 46 did not rise as
the liquid 10 surface level 9 rises, the depth, d, would increase and
therefore the water pressure around the movable plunger 46 would
increase, thereby increasing the flow rate through the system. To
implement a relatively constant flow rate, the floats 50/52 of the flow
control system 40 lift the movable plunger 46 as the liquid 10 surface
level 9 raises, thereby maintaining a relatively constant depth, d.

[0038]In order to prevent the movable plunger 46 from exiting the conduit
42, a mechanism that limits its travel is provided, for example the float
shafts 54/56 extend downward through bushings 72 or holes in limit arm(s)
70 and are terminated with stops 73. In some embodiments, the stops 73
are adjustable, for example, nuts on a threaded end of the float shafts
54/56. The present invention works equally well without a mechanism that
limits its travel and, when a limit is used, any mechanism for limiting
travel is anticipated.

[0039]In the embodiment shown, the floats 50/52 are adjustable by bending
of the float shafts 54/56 and/or the cross member 60/62 or by adjusting
the vertical position of the floats 50/52 on the float shafts 54/56 using
threaded float shafts 54/56 and fasteners (e.g. nuts) 51. Any number
and/or shape of floats 50/52 are anticipated. Although shown throughout
this description as spherical, other shapes of floats 50/52 are
anticipated including square or rectangular boxes, etc. It is anticipated
that, in some embodiments, there is but a single cross member 60. Other
structural arrangements are also anticipated that connect one or more
floats 50/52 to the movable plunger 46. Any structural arrangement,
whether adjustable (as shown) or fixed that includes a movable plunger 46
of any shape or size held within a conduit 42 and interfaced to a float
arrangement 50/52 is anticipated, including one that is a fixed unit
without any adjustable components wherein the floats are permanently
affixed to a member that is interfaced to the movable plunger 46.

[0040]In some embodiments, a secondary skimmer 80 is integrated into the
flow control system 40. In this, a secondary skimmer 80, such as a
section of conduit having an inner diameter greater than the outer
diameter of the conduit 42, is interfaced to the cross members 60/62 such
that, as the flow control system 40 raises and lowers, so does the
secondary skimmer 80. The intent is to reduce the outflow of floating
debris as the liquid 10 exits the flow control system 40. Since the
secondary skimmer 80 extends below the surface 9, liquid 10 from beneath
the surface 9 flows between the secondary skimmer 80 and the conduit 42,
reducing the amount of floating debris passing through the flow control
system 40. The secondary skimmer 80 is optional.

[0041]Referring to FIG. 3, sectional view of a system of a second
embodiment of a flow control system 100 will be described. In this
embodiment, the movable plunger 146 is integrated with a skimmer 180 and
placed over the holding box 26. The skimmer 180 has two functions: to
reduce floating debris, oil, etc. from exiting the drain conduit 24 and
to keep the movable plunger 146 in place on the holding box. One or more
float device 150/151 are attached to the flow control system 100. Any
number and shape of float devices 150/151 are anticipated including one
continuous float device encircling the outer area of the flow control
system 100. The flow control system 100 of this design is adaptable to
existing holding boxes 26 with little or no modification to the existing
holding boxes 26.

[0042]In some embodiments (not shown), mechanisms are added to the basic
design to limit the height of travel during high levels of liquid (e.g.
water) 10. For example, a chain is attached at one end to the bottom end
of the plunger 146 and at an opposite end to the holding box 26.
Additionally, in some embodiments, positioning mechanisms (not shown) are
added to keep the movable plunger 146 roughly centered in the holding box
26. Although shown installed on a holding box 26, it is anticipated that
the flow control system 100 be used on any similar structure.

[0043]The flow control system 100 operates under the same principles as
the first embodiment. In that the flow rate is proportional to the
area/space between the outer surface 145 of the movable plunger 146 and
the inner surface 25 of the holding box 26 and the depth, d, between the
surface 9 of the liquid 10 and the bottom surface of the movable plunger
146. Since the movable plunger 146 raises with the surface 9 by function
of the floats 150/151, the depth, d, remains substantially constant and
therefore the flow rate, too, remains substantially constant.

[0044]Referring to FIG. 4, a perspective view of a flow control system 100
of a second embodiment of the present invention will be described. In
this, the flow control system 100 is installed over a holding box 26.

[0045]Referring to FIG. 5, a perspective view of a flow control system 100
of the second embodiment of the present invention will be described. The
movable plunger 146 is of similar shape as the holding box 26, but has a
smaller cross sectional area, thereby providing a gap between the outer
wall 145 of the movable plunger 146 and the inner wall 25 of the holding
box 26. It is anticipated that in some embodiments, the cross-sectional
shape of the movable plunger 146 is similar to the opening shape of the
holding box 26 while in other embodiments, it is different. For example,
one particular movable plunger 146 has a round cross-sectional shape and
fits within a holding box 26 that has a square opening or visa-versa.

[0046]In some embodiments, the height of the movable plunger 46/146 is
determined based upon the height of the holding box 26 and the range of
expected liquid 10 levels. For example, if the systems of the present
invention need operate in a detention pond where a 3 foot range of liquid
10 levels is expected, then the movable plunger 46/146 is approximately 3
feet tall so that the bottom edge of the movable plunger 46/146 does not
exit the holding box 26 when the liquid 10 reaches its highest level.
Alternately, the flow control system requires stops to prevent the
movable plunger 46/146 from disengaging with the holding box 26 and
floating away such as the limit arms 70 and stops 71 of FIGS. 1 and 2.

[0047]Referring to FIG. 6, a sectional view of a system of the system 220
of a third embodiment of the present invention is shown. In this
embodiment, the holding box 26 is closed except for an opening in the lid
28 that holds an end of a stationary riser (conduit) 242. Within the
conduit/stationary riser 242 is a tapered plunger 246 that is suspended
by a shaft 255 from a support arm 260 that is interfaced to floats
250/252. As the level 9 of the water 10 in the detention pond rises, so
do the floats 250/252 and, through the support arm 260 and shaft 255, so
does the tapered plunger 246. Since the tapered plunger 246 is tapered,
when the level 9 of the water 10 is just above the lid 28, a larger flow
rate is permitted into the holding box 26 through the conduit 242 and as
the tapered plunger 246 lifts proportional to the level 9 of the water 10
as it rises, the tapered plunger 246 provides less water flow between its
wider circumference area and the inner circumference of the conduit 242.

[0048]The flow is controlled by the orifice equation:

Q=C*A*(2gH)**0.5

[0049]Where:

[0050]Q=flow rate

[0051]A=cross sectional area of gap between the tapered plunger 246 and
the conduit 242 (i.e. the gap area)

[0052]H=effective headwater depth

[0053]g=gravitational acceleration (32.2 ft/sec2)

[0054]C=orifice coefficient

[0055]Note: the effective headwater depth is the distance from the level 9
of water 10 to bottom 247 of the conduit 242 if the tailwater level (that
in the holding box 26) is below the bottom 247 of the conduit 242. If the
tailwater level (that in the holding box 26) is at or above the bottom
247 of the conduit 242, then the headwater depth is the distance from the
level 9 of water 10 to the tailwater level.

[0056]Referring to FIG. 7, a sectional view of a system of the system 222
of a fourth embodiment of the present invention is shown. In this
embodiment, the holding box 26 is has a lid 28 and at least one opening
32 that enables the flow of water 10 into the holding box as the level 9
of the water 10 raises above the opening 32. An internal shelf 29
supports a conduit 242 within the holding box 26. Within the conduit 242
is a tapered plunger 246 that is suspended by a shaft 255 from a support
arm 260 that is interfaced to floats 250/252 by float arms 257. As the
level 9 of the water 10 in the detention pond rises, so do the floats
250/252 and, through the float arms 257, support arm 260 and shaft 255,
so does the tapered plunger 246. Since the tapered plunger 246 is
tapered, when the level 9 of the water 10 is just above the lid internal
shelf 29, a larger flow rate is permitted into the holding box 26 through
the conduit 242 and as the tapered plunger 246 lifts proportional to the
level 9 of the water 10 as it rises, the tapered plunger 246 provides
less water flow between its wider circumference area and the inner
circumference of the conduit 242.

[0057]The flow is controlled by the orifice equation:

Q=C*A*(2gH)**0.5

[0058]Where:

[0059]Q=flow rate

[0060]A=cross sectional area of gap between the tapered plunger 246 and
the conduit 242 (i.e. the gap area)

[0061]H=effective headwater depth

[0062]g=gravitational acceleration (32.2 ft/sec2)

[0063]C=orifice coefficient

[0064]Note: the effective headwater depth is the distance from the level 9
of water 10 to bottom 247 of the conduit 242 if the tailwater level (that
in the holding box 26) is below the bottom 247 of the conduit 242. If the
tailwater level (that in the holding box 26) is at or above the bottom
247 of the conduit 242, then the headwater depth is the distance from the
level 9 of water 10 to the tailwater level.

[0065]As in the prior embodiments, any number of floats, shape of conduit
242 and tapered plunger 246 are anticipated.

[0066]Equivalent elements can be substituted for the ones set forth above
such that they perform in substantially the same manner in substantially
the same way for achieving substantially the same result.

[0067]It is believed that the system and method of the present invention
and many of its attendant advantages will be understood by the foregoing
description. It is also believed that it will be apparent that various
changes may be made in the form, construction and arrangement of the
components thereof without departing from the scope and spirit of the
invention or without sacrificing all of its material advantages. The form
herein before described being merely exemplary and explanatory embodiment
thereof. It is the intention of the following claims to encompass and
include such changes.